Eruption of the Eyjafallajökull Volcano at Island:

Reconstruction of the ash distribution over Europe between April 14 and 21.

Scientists from the GKSS Research Center confirm the predictions by the Volcanic Ash Center in London which had been frequently criticized by means of independent model simulations. In addition they provide estimates of ash particle concentrations. The model results were fortified by measurements.

By means of an independent simulation modeling system (COSMO-CLM/CMAQ) Scientists of the Institute for Coastal Research at the GKSS Research Center, Geesthacht reconstructed the temporal and spatial propagation of the ash plume over Europe between April 14 and 21 2010. The reconstructions confirmed largely the predictions of the spatial distribution of the plume that have been published by the Volcanic Ash Center, London. In addition, the GKSS-scientists were able to estimate the ash particle concentrations in different height levels

These quantitative findings could be fortified by comparing the aerosol optical depth, a measure for the thickness of the aerosol layer, derived from simulation results with measurements carried out at ground stations of the Aerosol Robotic Network (AERONET, see link below) at Hamburg, Helgoland, Leipzig, Cabauw, Lille and Chilbolton. The data of the measurement stations were compared to several simulation scenarios that differed concerning the strength of the ash emission. In this way conclusions about the probable emission strength, about which little is known so far, could be drawn. As the most probable scenario appeared an emission rate of about 4 tonnes ash per second as well as a significant decrease of the emissions after April 21.

Estimates of the ash particle concentrations were compared to the results of airborne measurements. A dedicated flight mission was conducted by the German Aerospace Center (DLR) on April 19 2010 between 15:00 and 18:00 UTC (DLR report, see link below). The comparison supported both the spatial pattern of the ash plume and the aerosol concentrations as simulated with the model. The aerosol concentration reached a maximum of 60 µg/m3 at a height of 4 km over the City of Leipzig whereas the air was relatively clean over the area between Hamburg and Leipzig. At the same time the model simulation suggested that the aerosol concentrations were likely to increase again over northern Germany during the hours following the flight mission.

The GKSS scientists conclude that these result underpin that only by combining measurements and model simulations it is possible to provide reliable information about both the temporal-spatial dynamic and concentration of volcanic ash.